It was a huge, glowing warhammer.
Moradin used this hammer both as a weapon and as a practical tool.
It was a warhammer +5.
Soulhammer was a one-handed warhammer of exceptional magical enhancement. It possessed the magical ability to be thrown effectively despite its size, and to return to its wielder. It was a sacred weapon, and struck with exceptional deadliness against evil and chaotic creatures.
Moradin created the lesser Hammer of All Souls in emulation of this hammer.